FIELD OF THE INVENTION
The invention relates to a bridge module having at least two bridge branches, at least two controllable semiconductor switches per bridge branch, a metal base plate with which electrically insulating and thermally conductive substrates provided with conductor tracks are connected, the semiconductor switches being electrically conductively mounted on the substrates, a housing having at least two AC terminals and DC terminals, AC connection leads connected to the AC terminals and to the semiconductor switches, and DC connection leads connected to the DC terminals and to the semiconductor switches.
Such bridge modules, for instance for three phases, are available on the market. As an example, reference is made to the Eupec catalog entitled IGBT-Module [IGBT Modules], print number 404W07/90. In the modules shown therein, the DC terminals of one and the same polarity are united in the housing and each is connected through one connection lead to DC terminals mounted on the housing. The DC lines from the DC terminals to the individual bridge branches are of various lengths. That asymmetry within the module limits the usable current and voltage range of the semiconductor switches, since the properties of the module are determined by the bridge branch having the highest parasitic inductance.